This application claims the benefit of Korean Application No. 2001-11731, filed Mar. 7, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical bench, and more particularly, to an optical bench with improved structure, in which an optical path is shortened and tolerance is high for misalignment of optical elements.
2. Description of the Related Art
Recently, with an increase in an amount of data transmitted through an optical communications network, data transfer methods for an optical communication system are changing to wavelength division multiplexing (WDM) transfer methods. As such WDM systems need a connection between networks and an optical crossing connector, i.e., an optical bench, which is considered an essential element of the WDM systems.
In a conventional optical bench, as shown in FIG. 1, a plurality of micro-mirrors 40 are arranged in a matrix on a substrate 10. The substrate 10 includes a plurality of input optical fibers 20, each transferring an optical signal to the micro-mirrors 40, and a plurality of output optical fibers 50, each receiving and transmitting an optical signal reflected from the micro-mirror 40. A plurality of input and output optical elements 30 and 60 for condensing and/or diverging an incident beam are arranged between the micro-mirrors 40 and the input and output optical fibers 20 and 50.
As shown in FIG. 2, the input and output optical fibers 20 and 50 are placed in parallel first V-grooves 25 arranged with a predetermined separation gap therebetween, and the input and output optical elements 30 and 60 are placed in second V-grooves 35 connected to the first V-grooves 25. The input and output optical fibers 20 and 50 are aligned with the input and output optical elements 30 and 60, respectively, along a line. The input optical fiber 20 and the input optical element 30 are aligned in one optical axis with the micro-mirrors 40 and the output optical fiber 50 and the output optical element 60 are aligned in another optical axis with the micro-mirrors 40.
For the optical bench having the configuration described above, a light beam emitted from a light source (not shown) enters one of the input optical fibers 20 and a corresponding input optical element 30. The light beam is then reflected by a predetermined micro-mirror 40. The light beam reflected by the micro-mirror 40 is output through one of the output optical elements 60 and a corresponding output optical fiber 50.
An optical path of an incident beam can be changed toward an intended output channel by positioning the micro-mirrors 40 flat or upright on the substrate 10. In particular, when the micro-mirrors 40 are positioned upright on the substrate 10, the incident beam is reflected by the micro-mirrors 40 towards the intended output channel. When the micro-mirrors 40 are positioned flat on the substrate 10, the incident beam goes straight, passing over the micro-mirrors 40 without being reflected.
When transferring the optical signal to the intended channel by changing the optical path, as described above, a minimum optical path is formed when an input optical signal received from, for example, an input channel ch_1, through the input optical fiber 20 and the input optical element 30, reaches the micro-mirror 40 nearest to the input optical element 30 through an optical path Sxe2x80x2, and is reflected by the micro-mirror 40. The optical signal is output through the optical path Sxe2x80x2, an output optical element 60a, an output optical fiber 50a, and an output channel ch_(N+1). In this case, the minimum optical path is formed as 2Sxe2x80x2.
Meanwhile, a maximum optical path is formed when the optical signal received from an input channel ch_N through an input optical fiber 20xe2x80x2 and an input optical element 30xe2x80x2 reaches a micro-mirror 40xe2x80x2 farthest from the input optical element 30xe2x80x2 through an optical path Lxe2x80x2, and is reflected by the micro-mirror 40xe2x80x2 and enters an output optical channel ch_(N+M) through an optical path Lxe2x80x2. Here, M is the number of output channels, and N is the number of input channels. Supposing M is equal to N, a maximum optical path 2Lxe2x80x2 can be expressed as formula (1), using the unit optical path Sxe2x80x2 and a channel pitch Pxe2x80x2 between each input and output optical element 30 (60):
2Lxe2x80x2=2(Sxe2x80x2+(Nxe2x88x921)Pxe2x80x2)xe2x80x83xe2x80x83(1) 
The channel pitch Pxe2x80x2 is greater than a diameter D of each optical element 30 and 60 because the input and output optical elements 30 and 60 typically do not perfectly fit into the second V-grooves 35 for the structural characteristic of the V-shaped grooves. Thus, the greater the diameter of the optical elements 30 and 60, the greater the channel pitch Pxe2x80x2 and the greater the maximum optical path 2Lxe2x80x2.
FIG. 3 shows the maximum optical path 2Lxe2x80x2 for each Nxc3x97N channel structure when the input and output optical elements 30 and 60 have a diameter (D) of 0.3 mm and 1 mm, respectively, and the unit optical path Sxe2x80x2 is equal to 1 mm. For this maximum optical path calculation, the channel pitch Pxe2x80x2 is determined to be 66% greater than the diameter (D) of optical element.
In FIG. 3, it is apparent that the length of the maximum optical path 2Lxe2x80x2 markedly increases with an increased number N of channels. For example, for a 128xc3x97128 channel structure, when the input and output optical elements 30 and 60 have a diameter (D) of 1 mm, the optical signal should travel a distance 400 times greater than the diameter (D) of the input and output optical elements 30 and 60. As the optical path becomes longer, optical path alignment becomes difficult. Thus, to maintain optical efficiency, an error in reflection angle of the micro-mirror, and an alignment error between the optical elements and optical fibers or between the optical elements and micro-mirrors should be precisely controlled to be small. As a result, manufacturing cost increases due to an increase in assembly expense.
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To solve the above-described problems, it is an object of the present invention to provide an optical bench with an improved structure in which optical fibers and optical elements are arranged in a staggered fashion to reduce a maximum optical path and tolerance for misalignment of the optical fibers or micro-mirrors becomes great.
To achieve the above and other objects of the present invention, there is provided an optical bench including: a substrate; input and output optical fibers arranged on the substrate with a predetermined separation gap therebetween, wherein far ends of the input and output optical fibers form a zigzag pattern to guide input and output beams; input and output optical elements arranged at the far end of each input and output optical fiber, respectively, condensing and/or diverging the input and output beams; and micro-mirrors receiving the input beam from the input optical elements and reflecting the received input beam toward predetermined channels.
The optical bench satisfies a relation of Pxe2x89xa6D, where P is a channel pitch and D is a diameter of the input and output optical elements.
The input optical fibers and the input optical elements, or the output optical fibers and the output optical elements are arranged on different planes.
The input and output optical fibers and the input and output optical elements are arranged as multiple layers and the arrangement for each multiple layer alternates.
To achieve the above and other objects of the present invention, an optical bench is provided, including: a substrate; input and output optical fibers arranged in a staggered pattern on the substrate guiding input and output beams; input and output optical elements arranged at a far end of each input and output optical fiber, respectively; and micro-mirrors receiving the input beam from the input optical elements and reflecting the received input beam toward the output optical elements.
These together with other objects and advantages, which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout.